Conventional attenuators typically are unitary or self-contained electromechanical units which have a relatively heavy housing formed with mechanical connectors at each end, and an attenuator circuit positioned within the housing. These attenuators are serially connected to audio signal lines which typically have mating connectors at the ends thereof proximate the attenuator so as to mechanically couple the audio signal lines to the mechanical connectors of the attenuator. Audio signal lines also commonly have mechanical connectors at the ends thereof distal or farthest from the attenuator for connection to audio or signal devices, for example a microphone or an amplifier, at the distal end of the line.
Thus, the two electrical devices are connected together by the two separate audio lines and the conventional attenuator such that there are at least four mechanical connections between the electrical devices.
FIG. 1 shows one example of a conventional attenuator 100 adapted to mechanically couple the ends of two separate audio signal lines (not illustrated) together. The attenuator 100 is relatively large and has a relatively heavy metallic housing 101 enclosing an attenuator circuit therein. The housing 101 has a male mechanical connector 102 and a female mechanical connector 103 at opposite ends thereof. The male mechanical connector 102 has a latch 104 which selectively secures the attenuator 100, and in particular, the male connector 102 thereof to a female connector (not illustrated) of one of the audio signal lines (not illustrated). The female connector 102 of the attenuator 100 has a slot 105 adapted to receive a selectable latch on a male connector (not illustrated) attached on the other of the audio signal lines (not shown). Thus, the attenuator 100 is mechanically connected to the audio signal lines (not illustrated) by the male mechanical connector 102 and the female mechanical connector 103.
To electrically connect the attenuator 100 to the audio signal lines, the mechanical connectors 102 and 103 connect the attenuator circuit contained in the housing 101 to the signal conducting wires thereof. In particular, the female mechanical connector 103 includes a plurality of pins, here shown partially by pins 106, which are received in slots (not illustrated) at the ends of conducting wires of one of the audio signal lines. The male connector 102 includes a plurality of conventional slots (not illustrated) which receive pins projecting from the other one of the audio signal lines. However, these mechanical connectors 102 and 103 form interference points along the electrical circuit created thereby at which points stray electromagnetic fields can introduce interference that causes significant noise to appear downline in the wiring system. The interface between two mechanically connected conductors can also introduce interference.
While FIG. 1 shows male and female mechanical connectors 103 and 102 on the attenuator 100, other attenuators may also have threaded mechanical couplings which have one end threaded into the housing of the attenuator. The opposite end of these couplings extends out from the attenuator housing and has external threads thereon for threaded engagement with a threaded connector that is attached to a signal line. Thus, the cable assembly extending from one electrical device to a second electrical device which is defined by an attenuator and two signal lines has six mechanical connections between the two electrical devices.
These types of connectors may also include ring nuts to more securely attach the threaded couplings to the signal line and attenuator. It is also known to use conventional coaxial jacks or coaxial connectors secured to the housing to attach the signal line thereto.
Examples of prior art attenuators are found in U.S. Pat. Nos.: 5,039,961; 4,779,064; 4,618,839; 4,060,780; 4,665,347; 3,260,971; 2,760,170; and 2,452,737.
Accordingly, it is an object of this invention to provide a shielded cable formed with an in-line attenuator between two lengths of cable. It is a further object that the cable be formed without additional detachable mechanical connectors connecting the attenuator to the two separate lengths of cable. It is still a further object that the inventive attenuator be integrally formed with the shielded cable.
It is also an object of the invention to provide a method for manufacturing the shielded cable with the inline attenuator such that the in-line attenuator is an integral part of the shielded cable.
In view of the foregoing, the inventive shielded cable includes an in-line attenuator circuit and two lengths of electrical cable which are electrically connected to the opposite end portions of the attenuator circuit so as to define the cable length. A hollow housing surrounds the attenuating circuit and has a compression coupling at each end of the housing for securing the housing onto the adjacent end portions of the cable so as to shield and protect the attenuator circuit therein without significantly altering the weight or flexibility of the shielded cable as a whole.
Other objects and purposes of the invention will be apparent to persons familiar with devices of this general type upon reading the specification and inspecting the accompanying drawings.